For example, Japanese patent No. 3754349 discloses a conventional technology related to a brushless direct current (DC) motor including an insulating material arranged in a slot of the stator and a slot opening between teeth, and a winding wire directory provided to the teeth from above the insulating material. The four corners of the rectangular insulating material are cut off to form diagonal portions. At the end of the insulating material located between the teeth, the diagonal portions are provided to be inclined with respect to the center line between the teeth. The insulating material is a polyester film with a thickness of 0.2 to 0.5 mm.
With this conventional technology, the insulating material is arranged in the slot opening between the teeth of the stator. Accordingly, the nozzle of a wire winding machine touches the insulating material while moving between the teeth. This causes friction with the insulating material, thereby reducing the insulating ability.